1. Technical Field of the Invention
The present invention relates to a thermal development apparatus which has a transporting section that transports a thermal development recording material, and an exposing section that exposes the thermal development recording material to form a latent image, and which heats the thermal development recording material after exposure to make the latent image visible.
2. Description of the Related Art
Mammography is an imaging technique which forms right and left breast images of a woman (hereinafter, such breast images are referred to as mammo images) for breast cancer screening or the like. Mammo images based on right and left mammo image data are finally made visible, and subjected to comparative observation by the doctor. In this observation, it is important to discern a slight difference between the images. Therefore, a mammo image is requested to have a high sharpness and a high resolution.
Recently, a medical system has been developed in which a radiographic imaging apparatus such as a CR apparatus is connected to a thermal development apparatus via a network, and mammo image data are supplied online from the radiographic imaging apparatus to the thermal development apparatus to develop a mammo image.
Here, the developed right and left mammo images are subjected to a diagnosis by the doctor in a mode where chest wall portions are butted against each other (i.e., in a mode where the right and left beasts are placed axisymmetrically).
The doctor comparatively observes the right and left mammo images which are hung on a schaukasten, and makes a diagnosis while discerning a slight difference between the images in shape and density. However, the diagnosis is based on the observation conducted with the naked human eye. In consideration of this, photographs of the right and left mammo images ought to be those which are formed so as not to cause visual unbalance. For example, the lengths of margins in the peripheries of the photographs are to be equal to each other.
As a related art technique for forming a photograph of right and left mammo images in which visual balance is considered, for example, an X-ray image forming method is disclosed in JP-A-2004-135856 (hereafter “JPA '856”). In the X-ray image forming method disclosed in JPA '856, when right and left mammo images are to be visualized on a single film, their layout positions are finely adjusted so as not to form margins, and the right and left breasts on the film are placed back to back in a manner where the chest walls overlap with each other, thereby obtaining an easy-to-read mammo image.
As described above, when mammo images are to be developed, a technique for reducing visual unbalance between right and left mammo images is necessary. From this point of view, the present inventor has variously studied current medical systems to clarify points to be improved. As a result, the following two items (first and second points to be improved) are clarified. Hereinafter, the study result will be described with reference to the drawings.
(First Point to be Improved)
FIGS. 4A to 4D are diagrams illustrating one of the points to be improved (dispersion of margins) in mammo image formation in the current mammography.
As shown in FIG. 4A, the underarm sides of the right and left breasts 2, 3 of a woman to be examined are “the outer sides (in the figure, indicated by thick lines)”. In discussion of a rotation process or the like of a photograph image, a reference of some sort is required in viewing of a photograph. Hereinafter, the reference is provided by indicating the outer side of a breast with a thick line. In the drawings attached to the specification, a mammo image data is illustrated as an image.
As shown in the left side of FIG. 4B, a CR apparatus obtains mammo image data Q21, Q22 which are produced by photographing the right and left breasts 2, 3. The mammo image data Q21 is obtained by photographing the right breast 2, and the mammo image data Q22 by photographing the left breast 3. In the figures, K1 and K2 denote the chest wall. Usually, a CR apparatus conducts a process of rotating the right or left (in this example, left) mammo image data Q22 by 180 degrees as shown in the right side of FIG. 4B, and thereafter transmits the mammo image data Q21, Q22 to a thermal development apparatus.
In the thermal development apparatus, a laser exposing process is applied to a thermal development recording material to form a latent image of a mammo image, and the latent image is made visual by thermal development. In the heat developing step, as shown in FIG. 4C, for example, a roll film of a thermal development recording material is transported in the direction of the arrow, a heating process is conducted by a heater disposed below a transporting path, and a process of cutting the rear end of the thermal development recording material film on which the visible image is formed is conducted. As a result of these processes, a photograph W21 or W22 on which the visible image is formed.
The lengths of margins (SP1) formed in tip end portions of the photographs W21, W22 are equal to each other because of the following reason. In the laser exposing process, the laser exposure is started after the elapse of a predetermined time period from detection of the tip end of the transported thermal development recording material film. The tip end can be accurately detected, and hence the margin amount at the tip end can be controlled fairly accurately. By contrast, margins (SP3, SP4) at the rear ends are dispersed because the cutting positions of the thermal development recording material film are varied. In the case where the margins in the rear end portions of the right and left photographs (W21, W22) are dispersed, when the chest wall portions of the right and left photographs are butted against each other, the margins of the butted portions of the photographs W21, W22 are dispersed (one of the portions: SP1, and the other portion: SP4) as shown in FIG. 4D. Therefore, a visual impression is so unbalanced that the doctor hardly makes a diagnosis.
The CR apparatus rotates the mammo image data of the left breast 3 by 180 degrees, thereby allowing the two photographs to be discharged to a discharge tray of the thermal development apparatus in a state where the directions of the outer sides coincide with each other as shown in FIG. 4C. Since the directions of the outer sides coincide with each other, the doctor is requested only to fix the outer sides of the two photographs to a schaukasten, in order to produce a state where the chest walls are opposed to each other. When the rotation process is not conducted, the doctor must fix the photograph of the left breast 3 discharged from the thermal development apparatus, to the schaukasten after manually rotating the photograph by 180 degrees. This operation is cumbersome. In a CR apparatus, in order to enable the doctor to efficiently make a diagnosis, a process of rotating one of right and left mammo image data by 180 degrees is usually conducted as described above.
(Second Point to be Improved)
The second point to be improved is uneven density due to the temperature distribution of the heater. FIGS. 5A to 5G are diagrams illustrating the other of the points to be improved (occurrence of uneven density) in mammo image formation in the current mammography.
FIG. 5A shows a heater 300 used in thermal development of a thermal development apparatus. The temperature distribution of the heater in the direction x which is perpendicular to a transportation direction of a thermal development recording material is not uniform as shown in, for example, FIG. 5B. When a latent image 1 of a breast is formed in a mode where the chest wall K1 is parallel to the transportation direction as shown in FIG. 5C, uneven density occurs in a photograph W20 after thermal development as shown in FIG. 5D, because the temperature of a middle portion of the heater 300 is high. In FIG. 5D, a high density portion is hatched (this is applicable also to the subsequent figures).
Actually, mammo image data Q21, Q22 which are output from the CR apparatus, and which are as shown in FIG. 5E are subjected to the thermal development. Breast latent images 2, 3 are formed on the basis of the mammo image data Q21, Q22 in a mode where the chest walls K1, K2 are parallel to the transportation direction as shown in FIG. 5F, and then thermal development is implemented. As a result, uneven density occurs in the photographs W21, W22 after the development. Thereafter, the photographs W21, W22 of the right and left breasts are fixed to a schaukasten in such a manner that the chest walls K1, K2 are opposed to each other as shown in FIG. 5G. In the resulting photographs, the density relationships in the right and left mammo images are opposite to each other, and an unbalanced visual impression is produced. Therefore, the doctor hardly makes a diagnosis.